Lab Chat: How cells that see color are made

BIOLOGISTS GREW HUMAN RETINA TISSUE TO LEARN HOW CELLS TO SEE IN COLOR ARE MADE. (JOHNS HOPKINS UNIVERSITY)

Scientists grew retinas from stem cells for a year to create organoids that mimic human fetal development. These retinal organoids made three types of color-detecting cone cells that sense blue, green, or red light — in the same sequence as human retinas, the first major finding that used organoids and one that could speed research on therapies for eye diseases. Here’s what Robert Johnston of Johns Hopkins told me about the study, published in Science.

What did you discover?

We found the key mechanism to decide whether these cells are blue or red or green: The thyroid controls this. Early on, there are genes that lower thyroid hormone to generate blue cells and, later, different genes activate thyroid hormones to make red and green cells.

What does this mean for diseases that cause vision loss?

Macular degeneration is one of the things we think this will apply to down the road. The macula is responsible for about 50 percent of your total vision. It’s almost all color-detecting cone cells, so we hope our studies will help us understand not only how the macula is made, but perhaps down the road provide therapy for those suffering from macular degeneration.